1 Field of Invention
The present invention relates to a reactor for the continuous production of charcoal for use in the steel and iron industry (Blast Furnaces), said reactor having a substantially vertical structure and comprising, in sequence, a top charging zone, a drying zone, a carbonization zone, a cooling zone and a discharge zone, wherein the charging zone has a smaller cross section than the drying zone and has an extension into the drying zone, forming an annular space around the extension, in which space the wall of the drying zone has an outlet to a gas extraction line for the recirculation of these gases into the reactor.
2 Description of Related Art
Reactors for the continuous production of charcoal are well-known, for example, from documents FR 2,416,931, U.S. Pat Nos. 5,584,970 and 1,739,786.
FR 2,416,931 discloses a process for the continuous production of charcoal in a moving bed reactor, comprising a reduced section charging stack H, wherein the level of wood is periodically controlled to ensure that the stack is constantly charged with wood. Then a vat C with a substantially larger section is provided, wherein the wood is progressively dried and then carbonized under the effect of the hot gas coming from the lower section of said vat. The pyroligneous vapors are evacuated from the vat through an extraction line and conveyed into a chamber F which connects to a lower section of the vat C, into which chamber the hot gases coming from a heatexchanger E are simultaneously injected. The gas products are evacuated from a chamber D, located essentially at the same level as chamber F, and conveyed to a space connected to the heat exchanger E. Below the carbonization zone of the vat C is a compartment R for cooling the charcoal by recycling the gas extracted from said compartment through a water-cooled line inside a column L and reinjecting it into the compartment.
U.S. Pat. No. 5,584,970 discloses a reactor comprising a charging chamber (2), a preheating zone (3) to dry the wood, a carbonization zone (4), an optional calcination zone (5) and a cooling zone (6). Annular chutes (28 and 38) having a conical shape are provided between the different zones, and the hot gas extracted at the outlet of the carbonization zone is circulated mixed with (colder) exhaust gas and reinjected around the chute located between the drying zone and the carbonization zone. The cooling gas that feeds the cooling zone is extracted around the lower cone and passed through a cooler. Exhaust gas containing combustible elements is extracted from the top of the preheating zone and partially transported to a combustion chamber (11), and the gas extracted from this chamber is used to preheat the air in heat exchangers (16 and 17) before being discharged.
In particular in FR 2,416,931, and on a smaller scale in U.S. Pat. No. 5,584,970, the charging zone has a smaller cross section than the subsequent preheating zone and partially projects into the latter, forming in this region a “double tube ”structure. As also disclosed in U.S. Pat. No. 1,739,786, this overlapping has the function of, during the extraction of the hot gases at the top of the preheating zone, keeping the wood charge off the gas outlet, thus preventing the sawdust from being conveyed into the gas conduit, consequently avoiding clogging and the need for frequent maintenance.